Continuous process of casting thin film



R. s. REYNOLDS 2,169,288

CONTINUOUS PROCESS OF CASTING TH Filed May 18, 1955 Aug. 15, 1939 IN FILM INVENTOR RzbhardflReynalds ATTORNEY Patented Aug. 15, 1939 UNITED sTATEs PATENT orrice ooNTmUoUs raocsss or CASTING rum Richard S. Reynolds, Glen Cove, N. 1.

Application May 18,

' 1 Claim.

derivative or rubber derivative films below a thickness of approximately .0008- of an inch, because of the difllculties involved in stripping such film from the medium upon which they are cast, and involved in their subsequent treatment and handling. Films formed by driving oil a volatile solvent and cast upon a heated revolving .drum or belt can be easily made oi a thinness of .0001 of an inch, but up-to this time it has not been feasible to form and strip such films at commercial speeds because of tearing and mutilating the filmjeven if such stripplng'could be accomplished thickness could not be subsequently treated and handled commercially because of thelack oif tensile strength of the film.- I l However, I have devised a continuous process for casting, strippingand handling"cellulosic'"tle-..

rivative or rubber derivative films far'belo'w10008 of an inch in thicknesst flhe'thina film is cast upon the usual rigid surfaceppreferably upon a revolving drum, in the common mannerlcwell known in the 'artJbut such filnix-possesses ;insni'- ficient tensile strength to betstrlppedi coinmer cially by itself from-the drums Therefore, I-pro- 4o vide a fieribleitpapen strip orgeothe'r; material "travelling at approximatelysithetsame'trrate 0 speed andn'in =.tliewsame-igeneral :direction as the drum or :metallics-beltwandordinarilymprovlded with an adhesivegriandsapplyz'such strip ioia'pa'per to'the filmsoithatthrgtwobfirmlyzhdhere one to the other and: rorma fiexiblexlaminatedmat'e'ria adapted to behandlediandirolledrlikezpaper;'zcThe tensile strenstli: oi :the -:.;paper:2-ba1cke'1'rt--.orv strip should; b'esu mcient to' liftthexfihni irom the casting. medium-r: commerciallylawlthout solutipntiqii irubbemhydrqehloride in chloroform readily forms a transparent film wt en the volacommercially for films below .0008." thickness, it 1 has generally been accepted that films below such a 1935, Serial No. 22,191

tile solvent is driven of! by heat and there is a phase at which the solvent has been largely driven oil when the heated rubber hydrochloride film is slightly tacky due both to its solvent content and its thermoplastic qualities.

Where this rubber hydrochloride'film has insumcient strength for normal commercial stripping and handling, a stripping means ordinarily comprising a. paper backer which'may have a slight amount of adhesive thereon, is pressed against the film so that it will adhere thereto. 'I'hereupon, the paper and rubber hydrochloride film which adhere together in laminated form can be stripped as an integral unit from a' drum or belt without danger of tearing or mutilating the thin film. The lack of tensile strength in i the rubber filmis compensated by the tensile strength of the paper, thereby allowing commercial handling or the laminated combination. It is manifest that a lesser amount of material is used when films of insuillcient tensile strength are bonded and removed from the medium upon which they are cast by a backing means which supports them in the stripping operation; this allows important economies not heretofore realized, and applies both to cellulosic derivative film as well as to rubber derivative film. There are 1 many uses for such laminated material.

dling qualities could be used in place 01" the paper backer .tg strip films oi insumcient tensile strength from the medium upon which they are gc'ast; It is well recognized that where the film ,solutlon is directly applied to the paper that the latter; absorbs the film to a degree, and the film is'not smooth and even;v in fact, the film when thinfwill often have holes through vthe same.

It;is further apparent that where laminations of cellulosic derlvative or rubber derivative film andgpaper, or material having similar appropriate qualities, is desired that the continuous procwhen the latter is. on a drum is highly desirable; Mlticularly vbecause the lamination oi the film is aooomplished upon the same medium upon which it is cast, and so a minimum of handling oi'.;-the;fi1m by itself is required; and also because where; the film is cast directly "upon' a paper the paper'itends to absorb the film in considerable quantity due to the penetrative action of the solvent, in fact such absorption :may proceed at a rate which actually destroys the effect 01' the film layemaking holes, therein and I have found 1 thisztobe particularly/true where fibers in a rough paper tend to protrude through the surface of the-:film when cast directly upon a paper to form a laminatlon; a further addedadvantage of di- Also it is apparent that any fiexible materm having the necessary tensile strength and han- 1 essjof directly applying the paper to the film ectlywlaminating; paper and film castupon a drum is that the film has a fine highly polished surface or gloss due to the polished surface of the drum.

As, is well known, rubber'hydrochloride is insoluble in and resists the action of petroleum oils, alcohol, water, cold benzol and many other common substances, and therefore the advantage of obtaining a lamination of paper and thin hydrochloride rubber film of insufiicient tensile strength for ordinary commercial handling by itself, is manifest. Also the advantage of my one-step process of casting and laminatingfilm, and particularly waterproof film, upon a drum and laminating the same with paper, will be recognized, where such film is of the type having sufilcient or insufficient tensile strength for ordinary commercial handling.

My invention can be readily understood from the accompanying drawing which is set forth merely for the purpose of illustrating one particular embodiment of my invention, and there-- fore neither the drawing nor the embodiment is to be deemed as limiting the scope of my invention.

In the drawing, Fig. l is a diagrammatic sec tional view of a film casting drum together with a paper combining attachment, with certain of the parts shown in elevation; Fig. 2 is an enlarged fragmentary sectional view of a part of the apparatus shown in Fig. 1, indicating a paper backer being applied to a mm and stripping the same from a drum, and Fig. 3 is a greatly enlarged fragmentary section of a completed laminated product made in accordance with my invention.

In these figures a film Ill containing a derivative of rubber is cast upon a rigid smooth surface I2 of a drum [4,. the latter preferably bein of the. film casting type heated to drive off volatile solvents, as is well understood in film casting. A working example of a suitable rubber derivative film is an 8% rubber hydrochloride solution in chloroform cast by hopper l8 upon the drum I 4, which drum may be about five feet in'diameter and may revolve about once a minute and may be heated to about 130 F. A' web of paper it may be unwound from a roll indicated as '20 and preferably is ledby suitable guide rolls indicated as 22 over an adhesive applying roll 24, so

that the necessary adhesive 28 is applied againstpaper against adhesive applying roll fl. 'Ihe paper'web I8 is then firmly pressed by an adjustable spring mounted roller 3. againstfilm ll upon drum H. In addition to the adhesive the pressure. of roller II and the heat of the film casting drum cause the paper and the film firmly to adhere one to another so that the film ll, of insufficient tensile strength itself for normal commercial handling, can be stripped from the drum I4 and subsequently processed .if desired. In the example given, the film l ordinarily will be stripped from the circular drum after revolving thereon through about 315 degrees of its circumference but it is obvious ,that thinness of film, speed ofrotation. and degree of heat are all factors which may be widely varied.

- Although not indicated in the diagrammatic showing of Fig. l, itis understood that spring mounted roller 3|, and preferably roll 24, a e

power-driven and that the speed of the paper is synchronized with the speed of rotation of the drum so that the paper i8 and the film Ill may travel at approximately the same rate. Otherwise a dragging effect might occur which would wrinkle the film.

After the paper I! and film l0 form a laminated product 32 theproduct as such may be further processed as desired, and in the example given the rubber hydrochloride film and paper product 32 in laminated form is led to a deodorlzer to be deodorized.

Any suitable adhesive'may be used, but I have observed that a good working adhesive is formed of 50% ethyl alcohol by weight, 37.5% copal gum by weight and 12.5% .diamyl phthalate by weight in which the rubber hydrochloride is insoluble.

While the the example of my invention given above concerns the formation of a high gloss rubber derivative film of insufficient tensile strength of itself for normal commercial handling, it is obvious that my invention can be equally as well applied to similar cellulosic derivative film and that in its broader aspects my invention concerns a continuous process for the formation of a laminated product, which latter comprises film of insufficient tensile strength for normal commercial handling which has a supporting backing means provided therefor which is used to strip the-same from the medium upon which the film is cast; Therefore my invention also concerns any high gloss film of insufilcient tensile strength for normal commercial handling cast upon a rigid surface and'stripped therefrom, firmly laminated by a thin layer of adhesive by heat and pressure to a backing means of such tensile strength as required to strip and carry the film. The backing means naturally can be any flexible means of the appropriate tensile strength, preferably paper or any sheet metal formed of animal or vegetable fiber or a metallic foil. In fact, the continuous process-disclosed herein is applicable to the formation of thin metallic foils of insufiicient tensile strength for normal handling upon rollers and the stripping of such metallic foils from saidxollers by means of a backing means and an adhesive thereon, whereby a laminated product is continuously formed on the roll where the foil is formed;

It .istherefore manifest that the specific illustrative embodiment of my invention hereinabove described is not to be deemed as limiting, and it is to be understood that various embodiments and modifications may be made within the spirit of the invention, and that such embodiments are within the scope of the appended claim.

What I claim is:

A continuous process for forming a fiexibie substantially waterproof laminated product comprised of a lamina of a relatively strong paper and a lamina of high gloss rubber hydrochloride film without penetration of.the latter into the former, which comprises first forming and substantiaily drying a uniform film of rubber hydrochloride less than .0008" thick and unadapted for normal stripping because of a lack of tensile strength, upon a highly polished rigid moving surface, applying an adhesive in which said film is not soluble to a strip of paper moving at ap- RICHARD s. REYNOLDS. 

